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California Renal Water Quality Atrol Board <br /> Central Valley Region <br /> Terry Tamminen Robert Schneider,Chair 0 <br /> Secretaryfor Arnold Schwarzenegger <br /> Environmental 11020 Sun Center Drive#200 Rancho Cordova,CA 95670-6114(916)464-3291 Governor <br /> Protection http://w .swrcb,ca.gov/mgcb5 <br /> TO: Brian Newman <br /> Senior Water Resources Control Engineer <br /> Gordon Boggs <br /> UST Program Manager <br /> FROM: James Barton <br /> Engineering Geologi <br /> DATE: 11 August 2004 <br /> SUBJECT: REPORT REVIEW, REQUEST TO SUSPEND GROUNDWATER PUMPAND <br /> TREATMENT, CLEANUP AND ABATEMENT ORDER NO. 5-00-700, <br /> FLAG CITY CHEVRON, 6421 CAPITAL AVENUE,LODI,SAN JOAQUIN COUNTY <br /> Background: To date, Flag City Chevron, 6421 Capitol Avenue,Lodi (Flag City, Figure 1) has complied <br /> with the Cleanup and Abatement Order No. 5-00-700 (Order) requirement to continuously operate the <br /> groundwater pump and treatment(GW P&T) system. Flag City has operated the GW P&T system since <br /> November 2000, and has remediated over 26,000,000 gallons of groundwater contaminated with Methyl <br /> tert-Butyl Ether(MtBE) under NPDES permit#CAG915001, General Order No. 5-00-119 for discharge <br /> to surface water. Prior to starting the GW P&T, groundwater flow direction was generally to the <br /> southwest,probably due to the pumping influence from a small public supply well located at Rocky's <br /> Restaurant. Groundwater flow direction since startup of the GW P&T system has been radially inward <br /> towards the site. <br /> I reviewed the 30 July 2004 Quarterly Report—Second Quarter 2004 (Report). The Report stated GW <br /> P&T is no longer a cost-effective remedy; and recommended suspension of the GW P&T system, with the <br /> evaluation of ozone sparging (injection) to remediate the remaining dissolved MtBE plume. MtBE <br /> concentrations in June 2004 from the five active GW P&T extraction wells ranged from 6.1 to 79 µg/L, <br /> with an average monthly influent concentration of 17 gg/L. The 2004 cost per pound of MtBE removed <br /> exceeds $60,000, approximately 5 times the cost per pound of MtBE removed after startup in 2000. <br /> Onsite monitoring wells, with the exception of MW-8 (120 µg/L), reported non-detect for MtBE <br /> (<0.5 gg/L). Additionally, the Rocky's Restaurant small public supply well has been abandoned and <br /> replaced with a deeper well,removing a former contaminant conduit to the deeper aquifer. Finally, offsite <br /> petroleum hydrocarbon plumes appear to be hydraulically influenced by the Flag City groundwater pump <br /> and treatment system(Figure 8). <br /> California Environmental Protection Agency <br /> pia Recycled Paper <br />